Method for applying a metallic flake finish

ABSTRACT

A METHOD FOR APPLYING A DECORATIVE, METALLIC FLAKE FINISH TO AN ARTICLE. THE METHOD COMPRISES THE STEPS OF: (1) HEATING THE ARTICLE TO ABOVE THE MELTING TEMPERATURE OF A PRESELECTED TRANSPARENT THERMOPLASTIC RESIN; (2) WHILE THE ARTICLE IS HOT, COATING THE ARTICLE WITH A MIXTURE OF ALUMINUM FOIL FLAKES AND THE THERMOPLASTIC RESIN IN POWDER FORM; (3) REHEATING THE ARTICLE UNTIL THE POWDERED RESIN IS FUSED; (4) WHILE THE ARTICLE IS HOT, ELECTROSTATICALLY COATING THE ARTICLE WITH A SECOND LAYER OF A POWDERED, TRANSPARENT THERMOPLASTIC RESIN; AND (5) REHEATING THE ARTICLE TO FUSE THE SECOND POWDERED RESIN COATING INTO A SMOOTH LAYER. A PRIMER COATING MAY BE APPLIED TO THE ARTICLE TO INCREASE ADHESION BETWEEN THE ARTICLE AND THE DECORATIVE FINISH. CELLULOSE ACETATE BUTYRATE IS A PREFERRED THERMOPLASTIC RESIN. THE PRIME-COATING MAY BE APPLIED EITHER IN LIQUID FORM BY SPRAYING, OR IN POWDERED FORM BY MEANS OF EITHER A FLUIDIZED BED OR AN ELECTROSTATIC   SPRAYER. THE POWDER COATING MAY BE APPLIED BY A FLUIDIZED BED.

Jan. 2, 1973 F. E. SPIELES 3,708,321

METHOD FOR APPLYING A METALLIC FLAKE FINISH Filed Sept. 18, 1970 APPLYLIQUID PRIMER COATING.

PREHEATTO DRY PRIMER COATING.

ELECTROSTATICALLY APPLY POWDER COATING OF A MIXTURE OF CLEARTHERMOPLASTIC MATERIAL AND METAL FLAKE s.

HEAT T0 FUSE THERMOPLASTIC POWDER.

ELE CTROSTATICALLY APPLY POWDER COATING OF CLEAR THERMOPLASTIC IMATERIAL HEAT T0 FUSE THERMOPLASTIC POWDER TO A SMOOTH COATING.

INVENTOR. FRANKLIN 5. 51 1212 5.

'ATTJ's.

United States Patent 3,708,321 METHOD FOR APPLYING A METALLIC FLAKEFINISH Franklin E. Spieles, Delphos, Ohio, assignor to HaganManufacturing Company, Deiphos, Ohio Filed Sept. 18, 1970, Ser. No.73,423 Int. Cl. Bb 5/02; B44d 1/092, 1/094 U.S. Cl. 11717 2 ClaimsABSTRACT OF THE DISCLOSURE A method for applying a decorative, metallicflake finish to an article. The method comprises the steps of: (1)heating the article to above the melting temperature of a preselectedtransparent thermoplastic resin; (2) while the article is hot, coatingthe article with a mixture of aluminum foil flakes and the thermoplasticresin in powder form; (3) reheating the article until the powdered resinis fused; (4) while the article is hot, electrostatically coating thearticle with a second layer of a powdered, transparent thermoplasticresin; and (5) reheating the article to fuse the second powdered resincoating into a smooth layer. A primer coating may be applied to thearticle to increase adhesion between the article and the decorativefinish. Cellulose acetate butyrate is a preferred thermoplastic resin.The prime-coating may be applied either in liquid form by spraying, orin powdered form by means of either a fluidized bed or an electrostaticsprayer. The powder coating may be applied by a fluidized bed.

BACKGROUND OF THE INVENTION This invention relates to coatings and, moreparticularly, to a method for applying a decorative, metallic flakefinish to an article.

Finishes are commonly applied to articles of manufacture both fordecorative purposes and for protection from corrosive and erosiveenvironments. Decorative finishes comprising light reflecting metallicflakes randomly dispersed in a transparent layer of paint have been longdesired, but have heretofore have diflicult and expensive to produce. Byvarying the flake size from large to small, the finish will vary fromone of high light reflectance that sparkles in both natural andartificial light to one having a jewel-like appearance. In the past,finishes of this type have been used primarily for custom-madeapplications, since the time and the required labor in applying thenumerous layers of the coating results in considerable expense. Metallicflake finishes have been seldom used for production lines because of theexpense. In a typical application, several primer coats are firstapplied to the article to be coated, the last of which may include acolor matching or contrasting the desired color of the completedarticle. Several coats of a transparent paint having colored flakes ofmetal dispersed therein are next applied until the entire surface area,or a high percentage of the surface area, is covered with the metallicflakes. Several coats of clear paint are then applied to completelyencompass the metallic flakes, and additional coats of the clear paintare applied with sanding between coats, until a smooth finish having adesired thickness and luster is produced. To achieve a satisfactoryfinish by this process, as many as twenty-two or more individual coatsmay be applied. Considerable time is also required, since the paint mustbe allowed to dry between many of the applications. To date, the bestfinishes of this type have been made with a clear acrylic based paint.However, the acrylic paint has not always held up in extremeenvironments.

Patented Jan. 2, 1973 Ice According to the present invention, animproved method is provided for applying to articles decorative andprotective finishes having a metallic flake appearance. The process issimpler and less expensive to use than prior art methods and isparticularly adaptable for use on continuous production lines. In apreferred embodiment, the finish comprises three fused coatings: aprimer coating, an intermediate coating of mixed metallic or lightreflective flakes and a transparent thermoplastic resin, and an outercoating of a transparent thermoplastic resin. The article being finishedis preferably preheated prior to applying the intermediate coating,which is applied as a powder. The powdered thermoplastic resin is fusedand the outer coating is applied, also as a powder and preferably whilethe article is hot. The finish is completed by fusing the outer coating.In a preferred embodiment, the intermediate and outer coatings areapplied by electrostatic spraying. However, other techniques such as afluidized bed may be used to apply the powdered coating. By usingelectrostatic techniques to apply the powder to a heated article, thesecond and third coatings can be made quite thick and the lightreflecting flakes will be randomly oriented, rather than flat. In apreferred embodiment of the invention, the thermoplastic resin iscellulose acetate butyrate which is applied as a powder for the secondand third coatings. However, in the broadest sense, any transparentthermoplastic resin having suitable properties for withstanding theenvironment in which the coated article is placed can be used for thecoating material. The primer, when used, may be any commerciallyavailable type recommended as a base for the particular thermoplasticresin used in the decorative finish. The light reflective flakes arepreferably of aluminum, but may be of any material which has a meltingtemperature appreciably above the melting temperature of thethermoplastic resin. When the resin is fused by heating the article, theapplied heat must not melt the light reflecting flakes.

Accordingly, the primary object of the invention is to provide animproved method for applying to an article a decorative finish having ametallic flake appearance.

Other objects and advantages of the invention will become apparent fromthe following detailed description, reference being made to theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single figure shows a simplifiedflow diagram of a process according to the preferred embodiment of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the singlefigure, a simplified flow diagram is shown for a preferred embodiment ofan improved method of applying to articles decorative finishes having ametallic flake appearance. The method has been found particularlyadaptable for coating small to medium sized metal articles on acontinuous, production line basis. The articles are first primed with asuitable prime material. The prime coating, which is optional, functionsto increase adhesion of the decorative finish to the article. The primematerial may be clear or, preferably, may have a pigment matching orcontrasting the color of light reflective flakes which Will be dispersedin the finish. The prime coating may be applied either in liquid form byspraying or painting, or in powdered form by means of a fluidized bed orof an electrostatic sprayer.

After the prime coating is applied to the article, the article ispreheated to evaporate any solvent in the primer and to facilitateapplying the decorative finish. While the article is still hot, amixture of a transparent, powdered thermoplastic resin and flakes of alight reflective material is applied to the article. Sufficient heatshould remain in the article to at least partially fuse or sinter thiscoating. The article is then heated to completely fuse the thermoplasticpowdered resin into a clear coating bonded to the randomly dispersedlight reflecting flakes and to the prime coating on the article. Whilethe article is still heated to a temperature above the meltingtemperature of the resin, a second coating of a transparent, powderedthermoplastic resin is applied. The article is again heated to fuse thesecond thermoplastic resin into a substantially smooth, continuouscoating. The second coating of the powdered resinous material ispreferably of a thickness to eliminate the roughness caused by therandomly oriented flakes in the prior coating.

The two coatings of powdered thermoplastic resin are applied byconventional techniques. Electrostatic spraying has been particularlyconvenient for applying uniform layers of the powdered coatings.Fluidized beds and charged fluidized beds have also producedsatisfactory coatings. When the powder coating is charged, it can beapplied to a cold article. However, preheating the article to above themelting temperature of the resinous coating material permits theapplication of a considerably thicker layer.

In a preferred embodiment, both the prime coating and the two powderedcoatings of thermoplastic resinous material are cellulose acetatebutyrate. Powdered resin of this type is available from Eastman ChemicalProducts, Inc. under the trademark Tenite. Cellulose acetate butyrate isparticularly desirable because it forms a tough, dimensionally stablecoating having long term resistance to weathering. However, it is withinthe scope of the invention to use other thermoplastic resins, forexample, acrylics, other cellulosics, ionomers, polypropylenes, andpolyvinyl chlorides. Given the desired properties of the finish as tostrength, wear and scratch resistance, moisture and chemical resistance,high and low temperature resistance, and other environmental conditionsto which the coated article will be subjected, the most suitablethermoplastic coating materials may be selected from, for example, theModern Plastics Encyclopedia, McGraw- Hill, Inc., vol. 46, October 1969.

The light reflecting flakes which give the finish a distinctiveappearance are preferably formed from aluminum foil. Such flakes arecommercially available in a wide range of colors and sizes. However,flakes of other metals such as steel foil may be used or flakes ofsilvered or colored resinous films may be used. Where the flakes areformed from resinous tfilms, they must have a melting point appreciablyabove the melting point of the thermoplastic material of which theobject is coated. Light reflective flakes of coated Mylar film having amelting temperature of approximately 480 F. may, for example, bedispersed in a cellulose acetate butyrate coating wherein the coating isfused by heating to a temperature in the range of 300 F. to 375 F.

To illustrate further the process of the invention, the followingexample particularly illustrates the process in finishing a specificarticle:

EXAMPLE A decorative, weather resistant finish was applied to metalflower vases of a type used in cemeteries and having a height ofapproximately nine inches. The vase was cast from a base metal. The vasewas initially sprayed with a bronze pigmented liquid primer. The vasewas then heated to 375 F. for approximately fifteen minutes tovolatilize the solvent from the liquid primer and to facilitate inapplying the next coating. While the vase was still hot, the vase waselectrostatically sprayed with a mixture having a ratio of four poundsof clear cellulose acetate butyrate to one pound of bronze coloredaluminum flakes until the exposed surface areas of the vase weresubstantially percent covered with randomly oriented aluminum flakes.The vase was then placed in an oven and heated to 375 F. forapproximately five minutes to melt the powdered cellulose acetatebutyrate. While the vase was still hot, the vase was electrostaticallysprayed with a coating of transparent cellulose acetate butyrate powder.The vase was again heated at 375 F. for approximately five minutes tofuse the latter powdered coating into a smooth coating extendingcontinuously over the outer surfaces of the vase. Upon cooling, the vasehad a bronze finish with a jewel-like sparkle and with excellent weatherresistant properties. The randomly oriented aluminum flakes gave thefinish a threedimensional appearance.

Although the powdered thermoplastic resin is preferably fused byheating, other techniques may be used. The powdered resin may, forexample, be melted by exposure to hot vapors of a suitable solvent.After the resin flows into a continuous, uniform coating, any absorbedsolvent is volatilized. It will be apparent to those skilled in the artthat many other variations may be made in the materials and applicationof the above-described coating method without departing from the spiritand the scope of the claimed invention.

What I claim is:

1. A method for applying a decorative finish to an article comprisingthe steps of applying a solvent-containing primer coating to thearticle, evaporating the solvent from the primer coating by heating thearticle to an elevated temperature between 300 F. and 600 F.,electrostatically applying, while the article is still hot, 'anintermediate coating consisting of a mixture of one part by weight ofdecorative light-reflective aluminum foil flakes and substantially fourparts by weight of powdered transparent cellulose acetate butyrate resinon the article, melting the transparent resin by heating the article toan elevated temperature between 300 F. and 480 F., electrostaticallyapplying, while the article is still hot, an outer coating of powderedtransparent cellulose acetate butyrate resin on the article and heatingthe article to melt the outer coating to form a smooth transparentfinish over the intermediate coating.

2. A method according to claim 1, wherein the primer coating has a colormatching the color of the aluminum foil flakes.

References Cited UNITED STATES PATENTS 2,004,567 6/1935 Brumbaugh 41362,748,019 5/1956 Schramm 117-31 2,931,736 4/ 1960 Park 1179 2,974,060 3/1961 Dettling 117-21 3,010,845 11/1961 Schornstheimer 117-7 1 3,085,0254/1963 Eaton 1179 3,117,886 1/1964 Glynn 11745 3,264,132 8/ 1966 Merrillet al. 11731 3,399,070 8/1968 Scharf 1174 3,490,934 1/1970 Oakley et a1.117-18 3,194,675 7/1965 Carter et a1. 11729 3,377,183 4/ 1968 Hurt eta1. 11717 3,336,903 8/ 1967 Point 11717 X 3,140,195 7/1964 Nagel 117213,513,012 5/1970 Point 11717 3,351,504 11/1967 De Hart 11721 X 3,028,2514/1962 Nagel 11721 3,546,017 12/ 1970 Pendleton et a1. 117-21 X WILLIAMD. MARTIN, Primary Examiner M. SOFOCLEOUS, Assistant Examiner US. Cl.X.R.

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